docs: def modify(self, symbol, base_value):
          """
          Change the base value of a unit symbol.  Useful for adjusting code
          units after parsing parameters.
  
          Parameters
          ----------
  
          symbol : str
             The name of the symbol to modify
          base_value : float
             The new base_value for the symbol.
  
          """
          self._unit_system_id = None
  
          if symbol not in self.lut:
              raise SymbolNotFoundError(
                  "Tried to modify the symbol '%s', but it does not exist "
                  "in this registry." % symbol
              )
  
          if hasattr(base_value, "in_base"):
              new_dimensions = base_value.units.dimensions
              base_value = base_value.in_base("mks")
              base_value = base_value.value
          else:
              new_dimensions = self.lut[symbol][1]
  
          self.lut[symbol] = (float(base_value), new_dimensions) + self.lut[symbol][2:]